The present invention is directed to a data communication system which is suitable for multi-address switching.
Recently developed data terminals operate according to different data transmission procedures including signalling, data format and data transmission rate. More specifically, the present invention is directed to a circuit arrangement and method for multi-address switching of digital encoded signals between a calling data terminal and a variety of called data terminals operating with different data transmission procedures. The circuit arrangement is adapted for use with an electronic data switching system which system itself is not capable of setting up physical connections between data terminals of different types.
Methods for establishing multi-address switching between a calling data terminal and a variety of called data terminals under control of the data switching system are known in the art. In the U.S. Pat. No. 3,697,672 to Reisch there is disclosed such a method based upon a separate apparatus containing its own register adapted to receive all information, especially station numbers of data terminals to be called, which is necessary for establishing multi-address connections. This known circuit arrangment for multi-address switching is connectable on its input side over an outgoing line of a data switching system to the system itself. This line is seized through evaluation in the data switching system of a special service number dialed by the calling data terminal. The circuit arrangement for multi-address switching operation is connected to both a central control unit of the data switching system and the communication path to the calling data terminal and thereby to cause request, evaluation, and storage of the information required. Thereafter, the circuit arrangement for multi-address switching operations is physically connected on its output side to the data switching system over a number of incoming communication lines to the corresponding number of data terminals participating in the multi-address operation. These connections via the data switching system are established according to the principle of establishing a single connection.
The circuitry is complex and even complicated and results in a high load to the data switching system in establishing the required multi-address connections.
Furthermore, there have been recently developed data terminals operating with different data transmission procedures. The term "data transmission procedures" hereinafter is understood to include all kinds of circuitry and standards for performing signalling procedures and transmitting data with a specific data format at a specific data rate. Accordingly, data switching systems for digital telecommunication which have been recently developed are suitable for use with different communication networks to handle teleprinter traffic and other data traffic.
A digital switching system of this type is disclosed in the technical manual entitled Siemens System EDS, System Description, which is published and distributed by Siemens Corp., Iselin, N.J. and which is incorporated herein by reference. This known electronic digital switching system is capable of handling the above-mentioned different types of data traffic with one exchange, that is the hardware and software is designed to respond to different data transmission procedures for teleprinter traffic and other data traffic simultaneously. However, the constraint of having a complex structure for different signalling, data format, and data rate, restricts the use of one exchange to physical connections within the respective groups of data terminals; that is, data terminals with different data transmission procedures cannot communicate with one another. Referring to multi-address switching operation, consequently only multi-address connections between similar data terminals operating with the same data transmission procedure can be established with known systems.
It is therefore, a main object of the present invention to overcome restrictions of data communication in known data communications systems, especially in establishing multi-address connections.
Another object of the present invention is to provide apparatus adapted for use with an electronic data switching system for establishing multi-address connections between data terminals of different types accordingly operating with different data transmission procedures.
Still another object of the present invention is to provide such an apparatus for establishing multi-address connections without a high burden on the data switching system.